Robotic arms with coaxially mounted helical spring means

Abstract

A robotic arm comprising a plurality of segments, each comprising articulated links, and means for causing each segment to bend so the arm can follow a serpentine path. A helical spring is provided coaxially with the arm to urge the links to an initial datum position, and to distribute the bending over the links of each segment.

1. A robot arm comprising:
 a plurality of longitudinal segments extending end-to-end to define a longitudinal axis of the arm wherein each segment comprises a plurality of links connected by articulated joints; 
 an actuator for a segment to control the shape thereof by causing or allowing the segment to bend by articulating between the links thereof; 
 a controller for controlling the actuator to cause or allow different segments along the arm to assume different or related shapes to define the desired spatial attitude of the arm; 
 characterized by at least one spring mounted coaxially with the arm and engaging with an engagement member on each of the links within a segment so as to cause the links to tend to an initial datum position, and to distribute the articulation amongst the links of the segment, in which the at least one spring is fixedly attached to each of the links by the engagement member along the longitudinal axis, the arrangement being such that the at least one spring may deform by bending to form an arc; 
 wherein the at least one spring engages with the engagement member along a helical path with respect to each of the links. 
 
     
     
       2. A robot arm as claimed in  claim 1 , in which the actuator is arranged to apply a compressive force to the links within a segment, and in which the at least one spring is arranged to apply tension to the links within the segments to reduce friction between links within said segment while maintaining a torsional stiffness. 
     
     
       3. A robot arm as claimed in  claim 1 , in which the at least one spring comprises a plurality of springs each of which operatively interconnects with each of the links within the segment. 
     
     
       4. A robot arm as claimed in  claim 1 , wherein the engagement members enable the links to be sequentially rotationally engaged with the at least one spring. 
     
     
       5. A robot arm as claimed in  claim 4 , comprising an end cap to engage with a first and a last link of the segment and with the at least one spring to contain rotation of the links with respect to the at least one spring. 
     
     
       6. A robot arm as claimed in  claim 1 , in which each link comprises a groove or series of teeth located on a helix to engage with the at least one spring. 
     
     
       7. A robot arm as claimed in  claim 6 , in which an unloaded pitch of the at least one spring is longer or shorter than a pitch of the engagement member on the links so that as the links are sequentially rotationally engaged with the at least one spring, the at least one spring is pre-tensioned or pre-compressed respectively, so as to urge adjacent links apart or together respectively. 
     
     
       8. A robot arm as claimed in  claim 7 , in which the spring has a different pitch at different positions along its length in order to vary the pre-tension or pre-compression in the at least one spring. 
     
     
       9. A robot arm as claimed in  claim 7 , in which the pitch of the engagement member on the different links is different in order to vary the pretension or pre-compression. 
     
     
       10. A robot arm as claimed in  claim 1 , in which the at least one spring is disposed externally about the links. 
     
     
       11. A robot arm as claimed in  claim 1 , in which the spring is disposed internally of the link assembly. 
     
     
       12. A robot arm as claimed in  claim 1 , in which the at least one spring comprises a plurality of springs. 
     
     
       13. A robot arm as claimed in  claim 1 , in which the arrangement of links and the connection of links constrain the at least one spring such that it can only bend to form an arc. 
     
     
       14. A robot arm as claimed in  claim 1 , in which the links are attached to the at least one spring by adhesive or by means of clamps or pins or by welding, or by mechanical key means. 
     
     
       15. A robot arm as claimed in  claim 1 , in which the links are arranged to constrain the degrees of freedom between adjacent links so as to limit the modes of deformation of the segments only to arcuate bending in response to operation of the actuator. 
     
     
       16. A robot arm as claimed in  claim 15 , in which the articulated joint is a ball and socket joint. 
     
     
       17. A robot arm as claimed in  claim 15 , in which the articulation between adjacent links is arranged to allow bending movement in only one plane in the manner of a hinge. 
     
     
       18. A robot arm as claimed in  claim 17 , in which the articulation between adjacent links are disposed at an angle with respect to each other. 
     
     
       19. A robot arm as claimed in  claim 17 , in which the articulation comprises a projection on the surface of one link arranged to engage with a corresponding depression on the surface of the adjacent link. 
     
     
       20. A robot arm as claimed in  claim 1 , in which there is approximately at least one complete wrap or coil of the at least one spring between engaging points on adjacent links. 
     
     
       21. A robot arm as claimed in  claim 1 , in which the actuator comprises three control wires for the control of each segment. 
     
     
       22. A robot arm as claimed in  claim 21 , in which each wire is attached to an actuator and extends from one end of the segment to the other, whereby operating the actuators to change the tension in the wires, causes or allows the links to flex thereby controlling the movement and shape of the segment. 
     
     
       23. A robot arm as claimed in  claim 1 , in which the at least one spring comprises one continuous spring along the length of the arm. 
     
     
       24. A robot arm as claimed in  claim 1 , in which each segment has a separate spring, the separate springs having different characteristics. 
     
     
       25. A robot arm as claimed in  claim 1 , in which the at least one spring comprises a first spring and a second spring concentric to the first spring and held in tension or in compression so that the links are constrained by both the first spring and the second spring. 
     
     
       26. A robot arm as claimed in  claim 1 , in which the at least one spring comprises two springs of the same diameter, each link engaging the springs. 
     
     
       27. A robot arm as claimed in  claim 1 , in which the at least one spring comprises a combination of two or more differently handed springs, with each link attached to all of the springs such that the rotary movement of a link with respect to one spring would result in a change in tension or compression in another spring, said change in tension serving to constrain further rotary movement of the links with respect to one another. 
     
     
       28. A robot arm as claimed in  claim 1 , in which the engagement member is selected from the group consisting of: a groove, a series of teeth, an adhesive, clamps, pins, a weld, a mechanical key and combinations thereof.